A map $f:X \to Y$ is *ring-like* if for every point $x \in X$ and every pair $U$ and $V$ of open neighborhoods of $x$ and $f(x)$ respectively, there is an open $W$ such that $f(x) \in W \subseteq V$ and $f^{−1}(\partial W) \subseteq U$. Ring-like maps were introduced by V. V. Fedorchuk in *Bicompacta with noncoinciding dimensionalities*, Dokl. Akad. Nauk SSSR 182 (1968), 275-277. Note that if $Y$ has a base of clopen subsets then any $f:X \to Y$ is ring-like. A ring-like map between compact spaces does not increase dimension (see Proposition 1.8 of [this article][1]). [1]: https://arxiv.org/abs/0805.2087